code: def test_multi_thread(self):
      n = 3
      augs = [
          naa.CropAug(sampling_rate=self.sampling_rate),
          naa.PitchAug(sampling_rate=self.sampling_rate),
      ]
  
      for num_thread in [1, 3]:
          for aug in augs:
              augmented_data = aug.augment(
                  self.audio, n=n, num_thread=num_thread
              )
              self.assertEqual(len(augmented_data), n)
  
file_path: nlpaug/test/augmenter/audio/test_audio.py
imports: import unittest
  import os
  from dotenv import load_dotenv
  import nlpaug.augmenter.audio
  from nlpaug.util import AudioLoader
label_desc: Use image node_id 2 for calling the TestAudio obj's underlying member method code with example usage: obj.test_multi_thread() without return types